Process control systems, like those used in chemical, petroleum or other processes, typically include one or more process controllers and input/output (I/O) devices communicatively coupled to at least one host or operator workstation and to one or more field devices via analog, digital or combined analog/digital busses. The field devices, which may be, for example, valves, valve positioners, switches and transmitters (e.g., temperature, pressure and flow rate sensors), perform functions within a process such as opening or closing valves and measuring process parameters. The process controllers receive signals indicative of process measurements made by the field devices and/or other information pertaining to the field devices, use this information to implement a control routine, and then generate control signals that are sent over the busses or other communication lines to the field devices to control the operation of the process. In this manner, the process controllers may execute and coordinate control strategies using the field devices via the busses and/or other communication links communicatively coupling the field devices.
Process control system applications typically include process control monitoring routines that can be configured to monitor various aspects of a process control system and to log information associated with monitoring the process control system. For example, monitoring routines are often used to monitor alarms associated with various field devices, modules, plant areas, etc. and to collect detailed information (e.g., instance/condition counts, time of day, acknowledged/unacknowledged status, duration, etc.) associated with the alarm. Monitoring routines may also be used to monitor other aspects of a process control system such as, for example, events, actions, errors, etc. The collected detailed information (i.e., process control log information) is typically stored in one or more centralized databases.
In a process control plant using a process control system, operating personnel and/or other process control plant personnel typically need access to the vast amounts of stored process control log information in order to safely and profitably operate the process control plant. Typically, users retrieve this information using, for example, data queries of the one or more databases in the process control system. The accessed data may be formatted into reports and displayed on a screen of a user interface, saved as a file, sent to another location, printed, or otherwise communicated or stored.
Often, operating personnel may desire to view data and information for related, non-contiguous time periods, for instance, data and information related to work teams, work shifts, or work groups. For example, operating personnel may wish to know the number of high temperature events that occurred during Team A's work shifts last month. In another example, operating personnel may wish to compare yield rates and number of tasks completed for different shifts.
In addition to personnel related information, users may with to determine information for other types of related, non-contiguous time periods. For example, a user may with to determine when Product XYZ was being produced last week. Other examples may include the number of failures for valves of type N in the last year, the average production rate, the percentage yield for a particular batch run type over the last year, and other such types of information.
Operating and other personnel, however, often encounter difficulty in trying to collect, consolidate and view report information over non-contiguous time periods of interest, especially in an easily obtained and meaningful manner. Frequently, the desired information is scattered across various databases and reports, sometimes even external to the process control system itself. For example, consider the case of viewing historical plant data associated with a particular team's work shifts. Most plants implement rotating shift schedules, where the varying start and stop times of the rotating shifts make it difficult and cumbersome to identify who was working at what time. Shift schedules may be incorporated into a human resources database which is independent of the process control plant system, and must be manually aggregated with historical process control data. Operating personnel may have difficulty in obtaining aggregate, average, percentage and/or total information over multiple, non-continuous time intervals given the inconsistent shift schedules and the disparately located data.
In fact, most control system reports, work shift-based or otherwise, are based on fixed time periods, relative time periods or scheduled time periods. If events of interest do not conform to the report time period structure, difficulty in identifying accurate time periods and adjusting report calculations may surface. Plant personnel are frequently forced to employ unwieldy, multi-step, manual data and report consolidation procedures in order to obtain desired data and information for multiple, non-contiguous time intervals.